linux-kernel - Re: [syzbot] [bpf?] KMSAN: uninit-value in bstr

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Date: Mon, 8 Apr 2024 22:33:24 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: syzbot <syzbot+f0d29b273acdcd3a2562@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, haoluo@...gle.com, john.fastabend@...il.com,
 jolsa@...nel.org, kpsingh@...nel.org, linux-kernel@...r.kernel.org,
 sdf@...gle.com, song@...nel.org, syzkaller-bugs@...glegroups.com,
 yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in bstr_printf

On 2/21/24 12:55 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    c1ca10ceffbb Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10e7f5f0180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
> dashboard link: https://syzkaller.appspot.com/bug?extid=f0d29b273acdcd3a2562
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/83d019f0ac47/disk-c1ca10ce.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/49e05dd7a23d/vmlinux-c1ca10ce.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/68ec9fa2d33d/bzImage-c1ca10ce.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+f0d29b273acdcd3a2562@...kaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in bstr_printf+0x19df/0x1b50 lib/vsprintf.c:3334
>   bstr_printf+0x19df/0x1b50 lib/vsprintf.c:3334
>   ____bpf_snprintf kernel/bpf/helpers.c:1064 [inline]
>   bpf_snprintf+0x1c8/0x360 kernel/bpf/helpers.c:1044
>   ___bpf_prog_run+0x2180/0xdb80 kernel/bpf/core.c:1986
>   __bpf_prog_run288+0xb5/0xe0 kernel/bpf/core.c:2226

#syz dup: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_lookup_elem

>   bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
>   __bpf_prog_run include/linux/filter.h:651 [inline]
>   bpf_prog_run include/linux/filter.h:658 [inline]
>   bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
>   bpf_flow_dissect+0x127/0x470 net/core/flow_dissector.c:991
>   bpf_prog_test_run_flow_dissector+0x6f4/0xa20 net/bpf/test_run.c:1359
>   bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4107
>   __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5475
>   __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]
>   __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]
>   __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5559
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> Uninit was stored to memory at:
>   bpf_bprintf_prepare+0x138d/0x23b0 kernel/bpf/helpers.c:1027
>   ____bpf_snprintf kernel/bpf/helpers.c:1060 [inline]
>   bpf_snprintf+0x141/0x360 kernel/bpf/helpers.c:1044
>   ___bpf_prog_run+0x2180/0xdb80 kernel/bpf/core.c:1986
>   __bpf_prog_run288+0xb5/0xe0 kernel/bpf/core.c:2226
>   bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
>   __bpf_prog_run include/linux/filter.h:651 [inline]
>   bpf_prog_run include/linux/filter.h:658 [inline]
>   bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
>   bpf_flow_dissect+0x127/0x470 net/core/flow_dissector.c:991
>   bpf_prog_test_run_flow_dissector+0x6f4/0xa20 net/bpf/test_run.c:1359
>   bpf_prog_test_run+0x6af/0xac0 kernel/bpf/syscall.c:4107
>   __sys_bpf+0x649/0xd60 kernel/bpf/syscall.c:5475
>   __do_sys_bpf kernel/bpf/syscall.c:5561 [inline]
>   __se_sys_bpf kernel/bpf/syscall.c:5559 [inline]
>   __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5559
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x63/0x6b
> 
> Local variable stack created at:
>   __bpf_prog_run288+0x45/0xe0 kernel/bpf/core.c:2226
>   bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline]
>   __bpf_prog_run include/linux/filter.h:651 [inline]
>   bpf_prog_run include/linux/filter.h:658 [inline]
>   bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline]
>   bpf_flow_dissect+0x127/0x470 net/core/flow_dissector.c:991
> 
> CPU: 1 PID: 8904 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-00331-gc1ca10ceffbb #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
> =====================================================